Analytical procedures to detect 2,3,7,8-TCDD at Seveso after the industrial accident of July 10, 1976

The analytical procedures used at Seveso (Milan, Italy) for the determination of 2,3,7,8-TCDD, and some isomers, in biological and environmental samples are reviewed in this paper. During the emergency period, up until the first 10 days of August, the extracts, mostly from soil or vegetation samples, were evaporated to dryness and then mixed with less than or equal to 10-ml solvent. Of these solutions, aliquots up to 10 microliter were injected into a low-resolution gas chromatograph (GC) combined with a low-resolution mass spectrometer (MS). Analytical sensitivity for vegetation and soil was less than 10 ppb and approximately 100 ppt, respectively--sufficient for the early mapping of the most heavily contaminated territory. After the emergency period, the greatest improvement in environmental sample analysis was the introduction of cleanup procedure which greatly reduced the presence of unwanted material in samples. Cleanup was followed by the complete removal of the solvent. Dry samples could be taken up with rather small volumes (greater than or equal to 0.1 ml) of solvent, of which an aliquot was used for GC-MS analysis. The instrumental setup was kept as above. For animal samples, extraction entailed preliminary alkaline digestion followed by a number of cleanup steps. The final dry sample was taken to desired volume by adding solvent (greater than or equal to 0.1 ml), of which a few microliters were injected in GC-MS apparatuses. Detection thresholds improved markedly and were less than 10 ppt for agricultural soil and sediment, less than or equal to 0.05 ppt for water, in the range of 60 to 200 ppt for air dust, less than 10 ng/m2 and 10 ppt for wipe and scrape tests, respectively, less than 50 ppt for vegetation, and 250 ppt for biological substrata. Major later improvements in TCDD assay were the use of high-resolution gas chromatography (hrGC-MS), in some cases combined with high-resolution mass spectrometry (hrGC-hrMS). This provided greater specificity, sometimes accompanied by a very marked increase in detection sensitivity.     

Developmental dental aberrations after the dioxin accident in Seveso

Children's developing teeth may be sensitive to environmental dioxins, and in animal studies developing teeth are one of the most sensitive targets of toxicity of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). Twenty-five years after the dioxin accident in Seveso, Italy, 48 subjects from the contaminated areas (zones A and B) and in patches lightly contaminated (zone R) were recruited for the examination of dental and oral aberrations. Subjects were randomly invited from those exposed in their childhood and for whom frozen serum samples were available. The subjects were frequency matched with 65 subjects from the surrounding non-ABR zone for age, sex, and education. Concentrations of TCDD in previously analyzed plasma samples (zone ABR subjects only) ranged from 23 to 26,000 ng/kg in serum lipid. Ninety-three percent (25 of 27) of the subjects who had developmental enamel defects had been < 5 years of age at the time of the accident. The prevalence of defects in this age group was 42% (15 of 36) in zone ABR subjects and 26% (10 of 39) in zone non-ABR subjects, correlating with serum TCDD levels (p = 0.016). Hypodontia was seen in 12.5% (6 of 48) and 4.6% (3 of 65) of the zone ABR and non-ABR subjects, respectively, also correlating with serum TCDD level (p = 0.05). In conclusion, developmental dental aberrations were associated with childhood exposure to TCDD. In contrast, dental caries and periodontal disease, both infectious in nature, and oral pigmentation and salivary flow rate were not related to the exposure. The results support our hypothesis that dioxins can interfere with human organogenesis.     

Mortality in a population exposed to dioxin after the Seveso, Italy, accident in 1976: 25 years of follow-up

The Seveso accident in 1976 caused a large, populated area north of Milan, Italy, to be contaminated by 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). In this study, the authors followed up the exposed population for chronic effects; this paper reports the results of the mortality follow-up extension for 1997-2001. The study cohort includes 278,108 subjects resident at the time of the accident or immigrating/born in the 10 years thereafter in three contaminated zones with decreasing TCDD soil levels (zone A, very high; zone B, high; zone R, low) and in a reference territory comprising surrounding, noncontaminated municipalities. Vital status and cause-of-death ascertainment were 99% complete. Adjusted rate ratios and 95% confidence intervals were calculated by using Poisson regression. Results confirmed previous findings of excesses of lymphatic and hematopoietic tissue neoplasms in zones A (six deaths; rate ratio = 2.23, 95% confidence interval: 1.00, 4.97) and B (28 deaths; rate ratio = 1.59, 95% confidence interval: 1.09, 2.33). These zones also showed increased mortality from circulatory diseases in the first years after the accident, from chronic obstructive pulmonary disease, and from diabetes mellitus among females. A toxic and carcinogenic risk to humans after high TCDD exposure is supported by the results of this study.     

Persistence of decreased T-helper cell function in industrial workers 20 years after exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin.

In experimentally exposed animals 2,3,7,8-tetrachlorodibenzo-n-dioxin (TCDD) causes severe immunosuppression. However, the overall susceptibility of humans for the different pathological effects of TCDD has remained unclear. We examined the long-term effects of TCDD in 11 industrial workers who were exposed to high doses of TCDD for several years 20 years ago. Current TCDD body burdens were still at least 10 times higher (between 43 and 874 pg/g blood far) in these exposed persons than in the average German population. To evaluate possible TCDD-induced changes in the percentage of different lymphocyte subsets, we determined a large panel of lymphocyte subsets in the blood by flow cytometric analysis. Immunocompetence of T-and B-lymphocytes was tested by nitrogen (phytohemagglutinin, pokeweed mitogen)- induced lymphoproliferation assays and by assays using sensitive mixed-lymphocyte cultures. No significant differences could be detected between the individuals tested and controls for surface marker distribution or mitogen-induced lymphoproliferation TCDD-exposed subjects showed a reduced response to human lymphocyte antigen-allogeneic lymphocytes and interleukin-2-boosted proliferation. Responder cells of the dioxin-exposed persons proliferated less in response to irradiated stimulator cells (p < or = 0.05), and the third-party mixed lymphocyte reaction against unirradiated stimulator cells revealed suppressive activity in the responder cell fraction compared to the controls (p < or = 0.01). Furthermore, the capacity of a pool of T cells isolated from TCDD-exposed subjects to proliferate upon interleukin-2 stimulation was significantly diminished (p < or = 0.05). TCDD has a long-term immunosuppressive-effect on T-helper cell function, which is mediated more likely by a reduced functionality of individual cells rather than by a reduction in absolute cell numbers in the peripheral blood.     

2,3,7,8-Tetrachlorodibenzo-p-dioxin toxic effects and tissue levels in animals from the contaminated area of seveso,Italy

After the environmental contamination by 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) in the area of Seveso, Italy, thousands of small domestic animals (mainly rabbits and poultry) died within a few weeks. Autopsies on dead animals showed various pathological signs, such as hepatic lesions and haemorrhage. TCDD was monitored in animal tissues by gas chromatography-mass fragmentography; rabbit liver levels corresponded fairly well to soil contamination, which indicated that this species can be used as a tool for tracking the presence of TCDD in the environment.     

Cancer consequences of the Chernobyl accident: 20 years on.

26 April 2006 marks the 20th anniversary of the Chernobyl accident. On this occasion, the World Health Organization (WHO), within the UN Chernobyl Forum initiative, convened an Expert Group to evaluate the health impacts of Chernobyl. This paper summarises the findings relating to cancer. A dramatic increase in the incidence of thyroid cancer has been observed among those exposed to radioactive iodines in childhood and adolescence in the most contaminated territories. Iodine deficiency may have increased the risk of developing thyroid cancer following exposure to radioactive iodines, while prolonged stable iodine supplementation in the years after exposure may reduce this risk. Although increases in rates of other cancers have been reported, much of these increases appear to be due to other factors, including improvements in registration, reporting and diagnosis. Studies are few, however, and have methodological limitations. Further, because most radiation-related solid cancers continue to occur decades after exposure and because only 20 years have passed since the accident, it is too early to evaluate the full radiological impact of the accident. Apart from the large increase in thyroid cancer incidence in young people, there are at present no clearly demonstrated radiation-related increases in cancer risk. This should not, however, be interpreted to mean that no increase has in fact occurred: based on the experience of other populations exposed to ionising radiation, a small increase in the relative risk of cancer is expected, even at the low to moderate doses received. Although it is expected that epidemiological studies will have difficulty identifying such a risk, it may nevertheless translate into a substantial number of radiation-related cancer cases in the future, given the very large number of individuals exposed.     

Age- and concentration-dependent elimination half-life of 2,3,7,8-tetrachlorodibenzo-p-dioxin in Seveso children

OBJECTIVE: Pharmacokinetic and statistical analyses are reported to elucidate key variables affecting 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) elimination in children and adolescents. DESIGN: We used blood concentrations to calculate TCDD elimination half-life. Variables examined by statistical analysis include age, latency from exposure, sex, TCDD concentration and quantity in the body, severity of chloracne response, body mass index, and body fat mass. PARTICIPANTS: Blood was collected from 1976 to 1993 from residents of Seveso, Italy, who were < 18 years of age at the time of a nearby trichlorophenol reactor explosion in July 1976. RESULTS: TCDD half-life in persons < 18 years of age averaged 1.6 years while those > or =18 years of age averaged 3.2 years. Half-life is strongly associated with age, showing a cohort average increase of 0.12 year half-life per year of age or time since exposure. A significant concentration-dependency is also identified, showing shorter half-lives for TCDD concentrations > 400 ppt for children < 12 years of age and 700 ppt when including adults. Moderate correlations are also observed between half-life and body mass index, body fat mass, TCDD mass, and chloracne response. CONCLUSIONS: Children and adolescents have shorter TCDD half-lives and a slower rate of increase in half-life than adults, and this effect is augmented at higher body burdens. RELEVANCE: Modeling of TCDD blood concentrations or body burden in humans should take into account the markedly shorter elimination half-life observed in children and adolescents and concentration-dependent effects observed in persons > 400-700 ppt.     

2,3,7,8-Tetrachlorodibenzo-p-dioxin in maternal breast milk and newborn head circumference

Dioxins are known to affect infant growth and neurodevelopment in both humans and animals. In this study, we examined the relationship between neonatal head circumference, which is related to fetal brain development, and the concentration of dioxins in breast milk as an indicator of maternal exposure. A total of 42 milk samples were obtained on the fifth to eighth postpartum day from mothers in Japan exposed to dioxins in the environment. The levels of seven dioxins and 10 furan isomers were measured in each milk sample using an HR-GC/MS system. The relationships between the concentration of each dioxin isomer and newborn size, including head circumference, were then investigated after adjustment for confounding factors. The concentration of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), the most toxic dioxin isomer, negatively correlated with newborn head circumference, even after adjustment for gestational age, infant sex, parity and other confounding factors. However, there were no significant relationships between the concentration of other dioxin and furan isomers in maternal breast milk and infant height, weight and chest circumference at birth. These facts suggested that fetal brain development might be influenced by maternal exposure to TCDD in the environment.     

北京市某垃圾焚烧厂周边大气二噁英污染特征及暴露风险

  目的   基于北京某垃圾焚烧厂的二噁英排放数据,评估其周边居民通过不同暴露途径面临的健康风险。  方法   参考美国加州热点计划,采用AERMOD模型,模拟北京某垃圾焚烧厂排放二噁英在大气中的扩散情况;借助多介质扩散模型,模拟二噁英在不同环境介质中的扩散情况;计算垃圾焚烧厂周边居民通过不同暴露途径的二噁英摄入量,评估人群终身致癌风险。  结果   在垃圾焚烧厂周边最大落地点浓度处,居民通过呼吸、皮肤接触、泥土摄入和母乳喂养等途径面临的终身致癌风险为5.28 × 10^–7;当居民饮用水来自于5大水库,饮食取自垃圾焚烧厂周边蔬菜基地、养殖场和水库时,所面临的终身致癌风险为1.77 × 10^–8。  结论   该垃圾焚烧厂在现有排放状况下,其周边居民面临的健康风险在充分安全边际内,其中呼吸和母乳喂养是最主要的暴露途径。     

Immunological abnormalities 17 years after accidental exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin.

Eighteen workers were reviewed 17 years after accidental exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin (dioxin). Clinical assessment showed that they were in good health. A study of several biochemical and immunological parameters in these subjects and in 15 carefully matched controls showed no difference in serum concentrations of hepatic enzymes between exposed workers and controls. Although mean serum concentrations of cholesterol and triglyceride were higher in exposed subjects than in controls, the results did not reach statistical significance. Antinuclear antibodies and immune complexes were detected significantly more frequently in the peripheral blood of workers exposed to dioxin. There was no significant difference between exposed workers and controls in the number of T lymphocytes, B lymphocytes, and helper and suppressor T cell counts in peripheral blood, but the number of natural killer cells identified by the monoclonal antibody Leu-7 was significantly higher in workers exposed to dioxin.     

Short- and long-term morbidity and mortality in the population exposed to dioxin after the "Seveso accident"

The early effects of 2,3,7,8-tetrachlorodibenzo-para-dioxin (TCDD) exposure in the population involved in the Seveso, Italy, incident in 1976, have been examined in numerous studies. Chloracne was the only effect linked with sufficient certainty to dioxin exposure. The possible long-term consequences were investigated with mortality and cancer incidence studies. Mortality and morbidity findings during the 20-year period following the accident showed increased risk from lymphoemopoietic neoplasm, digestive system cancer (rectum in males, and biliary tract among females, in particular) and respiratory system cancer (lung, among males). In the incidence analyses, also thyroid gland and pleura cancer appeared suggestively increased. Soft tissue sarcomas showed an increase in the largest, yet least exposed, exposure sub-cohort. Several hypotheses associating non-cancer effects with dioxin exposure were corroborated by findings in the Seveso population: this was the case with cardiovascular effects (possibly linked to both chemical exposure and stressful disaster experience), endocrine effects (diabetes among females) and reproductive effects: exposure of men to TCDD was linked to a lowered male/female sex ratio in their offspring. The results of many Seveso studies point to possible gender effects, in accordance with animal models. Notwithstanding the acknowledged study limitations (lack of individual exposure markers, short latency, and small population size for certain cancer types), results of previous experimental and epidemiological studies, along with mechanistic knowledge on dioxin toxicity, support the hypotheses that the observed excesses might be associated with dioxin exposure. The mortality and cancer incidence follow-up of the Seveso cohort are continuing.     

Pharmacokinetics of 2,3,7,8-tetrachlorodibenzo-p-dioxin in Seveso adults and veterans of operation Ranch Hand

A combined analysis of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) elimination in Seveso adults and Ranch Hand veterans found a period of fast elimination within the first 0.27 years after exposure in Seveso, followed by a period of slower elimination between 3 and 16.35 years from exposure. The mean TCDD elimination rate within the first 0.27 years after exposure among six adult males in the Seveso cohort was 2.0646 year(-1) (half-life=0.34 years). The mean rate from 3 to 16.35 years was 0.1011 year(-1) (half-life=6.9 years). The mean Ranch Hand elimination rate, 00924 year(-1) (half-life=6.9 years), measured between 9 and 33 years after exposure, was significantly less than the Seveso mean in the first 0.27 years after exposure, but not significantly different from the Seveso mean between 3 and 16.35 years after exposure. The fast elimination within the first 0.27 years followed by a slower rate after 3 years is consistent with the expected pattern in a two-compartment open model, with a distribution phase of rapid elimination followed by a slower elimination phase.     

2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) persistence in the Seveso (Milan, Italy) soil

Preliminary results of a new study on TCDD environmental persistence at Seveso (Milan, Italy) are presented. For this study, the most contaminated territory, Zone A, was divided into areas to fractionate the available TCDD levels in soil into data sets with reduced value spreads. In addition, various time subsets were defined for each area. Selected data were fitted with the exponential model y = y0.e-k.1. It was estimated that at least 1.2 kg TCDD was present in Zone A shortly after the accident. On average, a considerable portion (23%) of this amount lay on vegetation; TCDD which was not photodegraded or volatilized before the heavy rains of fall 1976, was later washed off and transferred to ground by water action. From this study, mean analytical underestimations affecting January 1977 and March 1978 contamination map data were on the order of 30 and 24%. All the above figures are considered optimistic. A few years after the accident, mean TCDD half-life in soil appeared to be 9.1y (t1/2-95% CLs, 6.2-17y).     

Thirty-four-year mortality follow-up of BASF employees exposed to 2,3,7,8-TCDD after the 1953 accident

Summary 2,3,7,8-Tetrachlorodibenzodioxin (TCDD) was formed in an uncontrolled decomposition reaction at BASF Aktiengesellschaft on 17 November 1953. This report presents the findings of a 34-year mortality follow-up study of 247 workers who were partly heavily exposed; 78 thereof had died. We divided these employees into three cohorts based on the amount and reliability of the exposure information. The mortality was compared with the national mortality rates in the Federal Republic of Germany (FRG) and is presented in terms of standardized mortality ratios (SMRs) together with 90% confidence intervals (CI) for different periods of time since the first exposure. In general, the overall mortality of these workers was similar to the rates of the national population. The SMR for all malignant neoplasms based on 23 deaths was 117 (90% CI: 80, 166), suggesting no overall increase in cancer among those employees. When workers with chloracne were examined separately, the SMR for all malignant neoplasms was not significantly elevated overall (SMR 139; 87, 211), but it was for the time period 20 or more years after the first exposure (SMR 201; 122, 315). Results for 22 causes of death as well as additional information on the type of exposure and skin findings are presented and discussed in relation to the current literature. In general, our results do not appear to support a strong association between cancer mortality and TCDD, but they do suggest that some hazard may have been produced.